Cambodian Prime Minister Hun Sen is trying to ease concerns over the social and economic costs of the country's plan with Australia to receive refugees. U.S.-based Human Rights Watch has called for the deal to be halted until Cambodia improves its refugee support system.

Hun Sen spoke out in defense of the refugee resettlement program in a letter he wrote last week to opposition politician Kem Sokha, the National Assembly’s first deputy president.

Cambodia’s Phnom Penh Post newspaper published details of the letter Monday, reporting the prime minister defended Cambodia’s ability to host the refugees, saying some 85 asylum seekers in a 2009 program from countries including Pakistan, Sudan, Myanmar and Vietnam have already been resettled.

He said services for the new arrivals would all be paid for by Australia through the $35 million resettlement program.

The agreement signed in September has been widely criticized by rights groups and the U.N. high commissioner for refugees, who have said that refugees in Cambodia already face steep financial and logistical hardships in the impoverished country.

Elaine Pearson, Australian director at Human Rights Watch, said Cambodia needs to reform its refugee resettlement program before people arrive under the Australian deal.

"The experience in Cambodia has been quite bad for these existing refugees. I mean they faced all sorts of problems. None of them have been offered proper residency documents and as a result at every step of the get-go they have to pay petty corruption and fines. A lot of them are unemployed, they are just staying at home. They don't want to be at risk of having to pay money to the Cambodian authorities," said Pearson.

Refugees that qualify for the Cambodia resettlement are presently housed on the Pacific island Nauru. They were already rejected for asylum status by Canberra under the Australian government's tougher policy towards people who arrive via boat.

Australia has been working in recent years to make it more difficult for asylum-seekers to reach its shores, arguing that many of the boat arrivals are economic migrants, not people in need of asylum. Authorities have also said that by cracking down on boat arrivals, they are discouraging human smugglers from making dangerous sea voyages.

Australia is planning to fund temporary accommodation and resettlement services for those refugees who voluntarily go to Cambodia, for at least one year, and then support on a case-by-case basis. Australia says it will also provide health insurance over five years.

But refugees in Cambodia have only an interim document - a prakas - confirming a right to stay in Cambodia, but insufficient for other official purposes, including opening a bank account.

Senator Sarah Hanson-Young, a member of the Green Party in Australia's parliament, conducted a week-long assessment in Cambodia this month and said the country is ill-equipped to deal with the needs of another group of vulnerable people.

"No matter whether they are legally here on the government books they won't be given jobs, they won't have access to local services without any type of formal recognized community ID card, they won't even be able to buy a sim card, buy a motorbike, open a bank account so someone could send them some money. They're being set up to fail," said Hanson-Young.

An Australian Catholic nun, Sister Denise Coghlan, who has worked in Cambodia since 1990, said the refugees will need trauma counseling, given the impact of detention in the Nauru camp and adjustment to Cambodia. Sister Coghlan fears Australia is setting a precedent in its dealings with refugees.

"I am really ashamed of Australia for offloading its responsibilities anywhere, but it's difficult to understand why they choose some of the poorest countries with a lot of poor people, to provide another group of people who will struggle in the beginning. I feel badly about that. Australia is setting an incredibly dangerous precedent if it starts selling off refugees," she said.

The Human Rights Watch report called on Australia to closely monitor implementation of the scheme and for the Cambodian government to work with relevant U.N. agencies and non-government groups to ensure the refugees are treated fairly and provide official assistance.